Mammalian interferons are valuable proteins useful in protecting and treating animals and humans from viral and other diseases, through the myriad actions of interferon (IFN). Marcus, Encyclopedia of Virology, 2:733-739 (1994); Krown et al., Encyclopedia of Virology, 2:739-745 (1994). The Food and Drug Administration has approved several uses of human IFN. Comparable studies with chickens and other avian species have been limited by the availability of chicken and avian IFN. Induction of avian interferon by virus has been successful in primary chick embryo cells xe2x80x9cagedxe2x80x9d in vitro, with yields of more than 100,000 units of IFN per 107 cells (Sekellick and Marcus, Methods in Enzymology, 119:115-125 (1986)), and chicken interferon (ChIFN) has been shown specifically to protect chicken cells against the lethal action of several viruses (Marcus and Sekellick, Virology, 69:378-393 (1976); Marcus et al., Journal of General Virology, 64:2419-1431 (1983)).
In addition it is possible that some important parasitic diseases of chickens like that caused by Eimeria may be controllable by interferon through its effects on the immune system. Interferon is gaining increased attention as an antiparasitic agent, (Murray, Journal Interferon Research, 12:319-322 (1992)).
Many factors determine how much interferon is induced by a particular virus. These factors include its origin and passage history, the host cell, incubation conditions and time, and the multiplicity of infection. Stewart, xe2x80x9cThe Interferon Systemxe2x80x9d, 2nd. ed., Vienna:Springer-Verlag, pp 27-57; Marcus, Sekellick and Nichol, Journal of Interferon Research, 12:297-305 (1992).
This invention relates to isolated genes and recombinant DNA coding for non-mammalian interferon, processes for preparing and isolating them and methods of use therefor. The isolated gene preferably codes for avian, fish or reptile interferon. Preferred embodiments of avian interferon include fowl, such as but not limited to chickens, ostrich, emus, turkeys, ducks, and exotic birds, such as parrots, cockatoos, cockatiels, and other commercially valuable birds. The nucleotide sequence encoding chicken interferon is described herein.
This invention also relates to a method of producing recombinant chicken interferon which comprises culturing a transformed microorganism capable of producing chicken interferon, said microorganism having inserted therein a recombinant chicken interferon gene such as the DNA sequence of SEQ ID NO: 1, (GenBank Accession No. U07868) and recovering said chicken interferon. The amino acid sequence encoding the signal and mature IFN protein has been deduced and is described herein (SEQ ID NO: 1) and SEQ ID NO:6. The mature IFN protein has been shown to be biologically functional. The transformed microorganism employed may be any host cell or cells capable of producing the recombinant protein. Preferably the host cell is derived from a eukaryote, mammalian cell culture or prokaryote, with eukaryote (e.g., insect cells) or mammalian cell culture (e.g., CHO cells) being most preferred in order to achieve glycosylation. Active material has also been obtained from E. coli. 
A cDNA probe is also described herein and comprises the nucleotide sequence of SEQ ID NO: 3. This cDNA probe, along with the cDNA of SEQ ID NO: 1, can be used to isolate and identify other non-mammalian interferon genes, such as other avian species, fish and reptiles, due to ancestral homology. A useful probe will comprise at least about a twenty base pair segment of the DNA sequence of SEQ ID NO: 1 which will bind to the complement of said sequence.
The invention also pertains to a plasmid comprising a) DNA sequence coding for non-mammalian interferon, preferably avian, fish and reptile interferon, most preferably chicken interferon, and b) a promoter sequence operably linked to said DNA sequence, preferably chicken metallothionein.
The novel plasmid constructs of this invention can be used to produce abundant quantities of recombinant interferon for administration to fowls and exotic birds, in order to prevent viral and/or parasitic infections. In another embodiment, interferon DNA can be introduced by genetic augmentation, i.e., genetic immunization. According to this method, DNA is introduced into the skin of the bird using a hand-held biolistic system (Sanford et al., Technique 3:3-16 (1992)) and serves as a template for manufacture of interferon. Tang et al., Nature, 356:152-154 (1992). Alternatively, the DNA and constructs containing the DNA of this invention can be used to produce transgenic fowl. The transgenic fowl would harbor an inducible plasmid for the transient expression of chicken interferon. Such transient expression would be induced at a time in the development of the fowl which would not retard growth but would provide protection against viral and/or parasitic infections.
This invention further pertains to transgenic fowl wherein its germ cells and/or somatic cells contain the recombinant DNA comprising an isolated avian interferon DNA introduced at an embryonic stage, and a method of making the same. Preferably, the recombinant DNA is substantially endogenous to the transgenic fowl, such as that coding for chicken interferon where the transgenic fowl is a transgenic chicken. In one embodiment, a promoter sequence heterologous to the chicken promoter can be operably linked to the recombinant DNA coding for chicken interferon in order to selectively induce expression of the interferon gene. An example of a heterologous promoter is the chicken metallothionein promoter which can be regulated by providing a source of metallic ions to the fowl. By this method, it is possible to treat or prevent viral and/or parasitic infection by inducing transcription of the DNA in the transgenic fowl.